[tip:sched/urgent] cpuset: Check if the cpus allowed is a subset of the cpuset's cpus for PF_THREAD_BOUND threads

[Dhaval Giani <dhaval@linux.vnet.ibm.com>]

Commit-ID:  5a98d36112f4301f068b638d6e0db2357f7deb75
Gitweb:     http://git.kernel.org/tip/5a98d36112f4301f068b638d6e0db2357f7deb75
Author:     Dhaval Giani <dhaval@linux.vnet.ibm.com>
AuthorDate: Thu, 12 Mar 2009 23:15:01 +0530
Commit:     Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 13 Mar 2009 00:21:25 +0100

cpuset: Check if the cpus allowed is a subset of the cpuset's cpus for PF_THREAD_BOUND threads

When a kernel thread which has been bound to a CPU is moved to
a cpuset which is a superset of the CPU it is bound to, the
movement fails.

 [root@llm11 cgroups]# mkdir a
 [root@llm11 cgroups]# echo 3 > a/cpuset.cpus
 [root@llm11 cgroups]# echo 0 > a/cpuset.mems
 [root@llm11 cgroups]# echo 12 > a/tasks
 [root@llm11 cgroups]# echo 12 > tasks
 -bash: echo: write error: Invalid argument
 [root@llm11 cgroups]# cat cpuset.cpus
 0-7
 [root@llm11 cgroups]#

(pid 12 is the migration thread bound to CPU 3)

Change the check to see if the cpus allowed is a subset of the
cpus allowed for that cpuset.

Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: menage@google.com
LKML-Reference: <20090312174501.GA7821@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 kernel/cpuset.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index f76db9d..34cfd46 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1362,7 +1362,7 @@ static int cpuset_can_attach(struct cgroup_subsys *ss,
 
 	if (tsk->flags & PF_THREAD_BOUND) {
 		mutex_lock(&callback_mutex);
-		if (!cpumask_equal(&tsk->cpus_allowed, cs->cpus_allowed))
+		if (!cpumask_subset(&tsk->cpus_allowed, cs->cpus_allowed))
 			ret = -EINVAL;
 		mutex_unlock(&callback_mutex);
 	}